Java中常用的加密算法有DES、AES、RSA等。以下是这些算法的应用示例：
DES加密算法的应用示例：import javax.crypto.*;import javax.crypto.spec.DESKeySpec;import javax.crypto.spec.SecretKeySpec;import java.security.InvalidKeyException;import java.security.Key;import java.security.NoSuchAlgorithmException;import java.security.spec.InvalidKeySpecException;public class DESExample { public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidKeySpecException, BadPaddingException, IllegalBlockSizeException { String plaintext = "Hello, world!"; String keyString = "mysecretkey"; // 密钥，长度必须为8字节 // 生成密钥 SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES"); DESKeySpec desKeySpec = new DESKeySpec(keyString.getBytes()); SecretKey secretKey = keyFactory.generateSecret(desKeySpec); // 创建加密器 Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE, secretKey); // 加密 byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes()); System.out.println("Encrypted: " + new String(encryptedBytes)); // 创建解密器 cipher.init(Cipher.DECRYPT_MODE, secretKey); // 解密 byte[] decryptedBytes = cipher.doFinal(encryptedBytes); System.out.println("Decrypted: " + new String(decryptedBytes)); }}import javax.crypto.*;import javax.crypto.spec.SecretKeySpec;import java.security.InvalidKeyException;import java.security.Key;import java.security.NoSuchAlgorithmException;public class AESExample { public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException { String plaintext = "Hello, world!"; String keyString = "mysecretkey123456"; // 密钥，长度必须为16字节 // 生成密钥 Key key = new SecretKeySpec(keyString.getBytes(), "AES"); // 创建加密器 Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE, key); // 加密 byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes()); System.out.println("Encrypted: " + new String(encryptedBytes)); // 创建解密器 cipher.init(Cipher.DECRYPT_MODE, key); // 解密 byte[] decryptedBytes = cipher.doFinal(encryptedBytes); System.out.println("Decrypted: " + new String(decryptedBytes)); }}import javax.crypto.Cipher;import java.nio.charset.StandardCharsets;import java.security.*;public class RSAExample { public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException { String plaintext = "Hello, world!"; // 生成密钥对 KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA"); keyGen.initialize(2048); KeyPair keyPair = keyGen.generateKeyPair(); PublicKey publicKey = keyPair.getPublic(); PrivateKey privateKey = keyPair.getPrivate(); // 创建加密器 Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); // 加密 byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8)); System.out.println("Encrypted: " + new String(encryptedBytes)); // 创建解密器 cipher.init(Cipher.DECRYPT_MODE, privateKey); // 解密 byte[] decryptedBytes = cipher.doFinal(encryptedBytes); System.out.println("Decrypted: " + new String(decryptedBytes)); }}以上示例分别演示了DES、AES和RSA加密算法的使用方法，包括生成密钥、创建加密器、加密和解密操作。请注意，密钥的长度必须满足算法要求，否则会抛出异常。加密和解密时使用的密钥必须匹配。
